/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/InfoTypes.h
Note that cycling or permuting the vertices of a triangle will change/break these indices.
struct FMeshTriOrderedEdgeID
int32
TriangleID
The index of the mesh Triangle
unsigned:  2
VertIndexA
The 0/1/2 index of the first vertex in the triangles tuple of vertices
unsigned:  2
VertIndexB
The 0/1/2 index of the second vertex in the triangles tuple of vertices